Why space fans are eyeing rockets in SpaceX launch

The unmanned Falcon 9 rocket being launched by SpaceX on a cargo resupply service mission to the International Space Station sits on the launch pad after an aborted liftoff from the Cape Canaveral Air Force Station in Cape Canaveral, Florida January 6, 2015.

SpaceX on Tuesday aborted another attempt at making a supply run to the International Space Station for NASA. But it's the rocket's return—not its takeoff—that has space fans talking.

Minutes after the planned launch from Cape Canaveral, the first stage of the unmanned Falcon rocket will aim for a vertical test landing on a barge in the Atlantic. The California company has attempted such landings on the open sea, but never on a platform like this.

SpaceX chief Elon Musk predicts a 50-50 chance of success at best. He says flying back boosters would allow them to be reused and save money.

NASA's previous delivery attempt by Orbital Sciences ended in a launch explosion in October. Researchers who lost experiments in the accident hustled to get replacements on this flight.